str1 = 'hello world'
str2 = "hello world"
str3 = "'hello world'"
print(str1)
print(str2)
print(str3)
print('hello\'world')  # 转义符

print('123{0}'.format(4))
print(f'{str1}{str2}{str3}')




for i in range(0, 101, 2):
    print("======开始下载======")
    if i == 100:
        print("开始下载")
    # else:
    #     print(f'{i}%','[',"*"*(i//2),"."*((100-i)//2),']')
    else:
        str4 = "*" * (i // 2) + "." * ((100 - i) // 2)
        print(f'{i}%{str4}')



